This invention relates to the formulation of a stable, water based solution of trihaloalkyl sulfone. More particularly, the invention relates to the formulation of a stable, water based microemulsion of bis(trichloromethyl)sulfone (BTCMS), a nonionic surfactant and a cationic quaternary ammonium halide surfactant.
Manufacturing as well as production processes use huge quantities of raw as well as potable water that must be treated with biocides in order to assure product and production standards. Typically, cooling towers, paper and pulp mills, canning industries, animal hide processing plants, secondary oil recovery using water flooding, industrial water systems, to name a few, require the use and recycling of the water used in these processes. These systems become easily contaminated with microorganisms such as bacteria, algae, fungi, etc., due to exposure to contaminants encountered in the process of manufacturing and/or from the products being processed. These waters become a breeding media for microorganisms which must be controlled and/or eliminated. Biocides have been developed which control such contaminants which if left unchecked, will destroy equipment and/or reduce the quality of a manufactured product.
Many biocidal formulations involve the use of organic solvents. However, there are growing objections to the use of costly organic solvents in formulating biocides. Of extreme concern is the ecological impact of these organic solvents. The organic solvents typically used, for example dimethylformamide (DMF), are toxic by themselves. In addition, these solvents can accelerate in the ability of a biocide to penetrate human skin, so that in the case of spills or accidental contact, the danger to human life is increased. Other problems posed by utilizing organic solvents are low flash point, hence a fire hazard, and excessive repulsive odors.
Economic problems are a concern when the biocides are formulated using organic solvents. Organic solvents cost more and they can present processing problems so that the effect is to increase the cost of biocidal formulations containing organic solvents.
Recent changes in Environmental Protection Agency (EPA) regulations present additional difficulties by requiring the removal of solvent based products from the marketplace. Action has already been taken by the EPA against DMF. It is anticipated that action against other commonly used solvents for biocide formulations may be taken.
Accordingly, there is a need for alternatives to organic solvent based biocide formulations. It has now been discovered that trihaloalkyl sulfone, (specifically bis(trichloromethyl) sulfone) a nonionic surfactant and a cationic quaternary ammonium chloride can be formulated as stable microemulsions in water. The formulas of the present invention have shown biocidal efficacy essentially equivalent to the solvent based formulas.
These formulas avoid the disadvantages associated with the use of organic solvents. The inventive formulas result in a reduced risk to human life through accidental skin exposure. These novel solutions can be prepared so as to contain a variety of concentrations of active ingredients. The technique involved readily permits the introduction of other water-soluble biocides into the product solution.
Biocidal compositions which have relied on water as the carrier fluid for the water insoluble, solid, active materials have been either dispersions or "oil-in-water" macroemulsions of the biocidal active material (sulfone) dissolved in a hydrocarbon solvent. Both approaches may have included surfactants as stabilizers, as well as possible additional materials which modify the viscosity in order to prevent separation.
The dispersed particles, or droplets in the case of an emulsion, are typically in the range of about 2 to 2000 microns, as taught by Slovinsky in U.S. Pat. No. 3,996,155. Dispersions and emulsions with this particle or droplet size range are inherently unstable. During prolonged storage, these types of products are subject to coalescence, aggregation and separation. The present invention solves this inherent instability by producing a thermo-dynamically stable microemulsion, where the water insoluble actives have been solubilized through the use of a combination of surfactants.
Microemulsions generally have droplets significantly less than about 0.3 microns (u). A microemulsion with liquid oils as the dispersed phase has a typical droplet size range of about 100 to 700 angstroms (1 angstrom=0.0001u) and so is a transparent solution. This size range is two orders of magnitude smaller than typical dispersions and macroemulsions. Particle size measurements on the present invention generally show the size to be less than about 300 angstroms.
U.S. Pat. No. 4,671,815, Bellos et al., discloses solubilized biocidal active materials utilizing surface active alkylamine hydrochlorides. However, this reference states that water should not be present at levels above about 1.5%, with the preferred level less than about 0.75%. When water is present above this limit, the biocidal active precipitates. This is not a limitation with a microemulsion.